Quantifying pentose cycle activity in intestinal mucosal leukocytes of hybrid striped bass (Morone saxatilis × M. chrysops)

Mucosal vaccines are promising for protecting fish from infectious diseases by stimulating immunity, but their success relies on understanding mucosal immunity's metabolic pathways. This study determined the ability of intestinal leukocytes to metabolize glucose through the pentose cycle (PC) as a potential energy source to support cellular functions required for mucosal immunity. Leukocytes were isolated from hybrid striped bass (HSB) at different development stages with mean body weights (BWs) of 14.2, 41.0, and 215.4 g. In addition, intestines from HSB with a mean BW of 41.0 g were divided into equal segments for proximal, middle, and distal regions. Leukocytes were incubated with oxygenated Krebs-Henseleit bicarbonate buffer containing either 5 mM D-[1- 14 C]glucose or 5 mM D-[6- 14 C]glucose at 26 ℃ for 2 h, and the 14 CO 2 produced from the leukocytes was collected to measure metabolism of glucose through the PC pathway. The glucose flux to the PC (nmol/2 h/10 6 cells) in leukocytes from HSB with mean BWs of 14.2, 41.0, and 215.4 g ranged from 40.7 to 47.5, 35.3–44.0, and 32.7–46.5, respectively. The glucose flux to the PC across different intestinal segments ranged from 35.2 to 41.1 in the proximal, 45.0–52.8 in the middle, and 39.9–46.4 in the distal. Both analyses reveal the preferential utilization of the PC for glucose oxidation ( P < 0.001 ). Collectively, these findings suggest that intestinal mucosal leukocytes of juvenile HSB support mucosal immunity by metabolizing glucose through the PC pathway as they develop from 40.7 to 215.4 g, and that the entire length of the intestine contributes equally to this metabolism.